This invention relates to the treatment of compact discs to remove the coatings normally applied to its polycarbonate substrate during manufacturing, and more particularly has to do with a method for the removal of such coatings in order to reclaim the polycarbonate.
As is well known, the compact disc is becoming an increasingly popular medium for the replication of audio programs. As currently manufactured, the compact disc comprises a thin circular polycarbonate substrate approximately 43/4 inches in diameter and having a central aperture adapted to be received on the centering mechanism of a disc player. Usually, the disc incorporates digitally encoded information on one surface thereof which is adapted to be laser-read by the disc player. The information-bearing surface of the substrate is coated with a thin film of aluminum which, in turn, is covered with a protective lacquer coating, of which two types are currently in common use. One is a cellulose nitrate based material in a suitable solvent such as toluene (so-called solvent based lacquer), and the other is an ultra-violet cured acrylic based material. Information regarding the programs recorded on the disc is printed in ink on the lacquer coating.
In the course of manufacture and distribution of such compact discs, many are scrapped as production rejects, or as a consequence of returns and inventory obsolescence, which presents a serious problem of disposal. Currently, they are either sold for scrap polycarbonate at a price which is very low (currently about $.01 per pound) because of contamination by the coatings or, if not salable at any price, discarded in a landfill. If the coatings are removed, the polycarbonate is more salable in that it can be re-used for the fabrication of compact discs or other parts and fetches a reasonable price, currently $.24 per pound, which at the same time, eliminates the need to landfill the scrapped discs.
The primary object of the present invention is to provide a process for removing the coatings from the polycarbonate substrate of compact discs so as to reclaim the polycarbonate.
Another object of the invention is to provide a process for treating compact discs to remove the coatings from its polycarbonate substrate that will free the protective lacquer coating regardless of its type.